During the processing of ore for the purpose of extracting minerals, numerous grinding, cleaning and separation processes are conducted. Most of the processing, such as grinding, is performed in water resulting in a mineral ore concentrate of the desired particle size in an aqueous suspension or slurry. The aqueous slurry is subjected to a filtering process to obtain dry ore concentrate for pelletizing or other purification processes.
One such filtration process utilizes a rotary disc filter 10, FIG. 1, that includes a plurality of generally fan shaped filter sectors 12 covered by a filter bag 22 or other type of filtering membrane. The filter sectors 12 are secured at close intervals around a rotatable support drum or shaft 14, for example, with a rod 16 and bracket 18. The filter sectors can then be rotated into and out of the slurry containing the concentrate or particulate matter to be filtered.
The disc filter 10 further includes conduits 20 to which the filter sectors 12 are fluidly connected. A vacuum is applied to draw water through the filter bag 22, into the filter sectors 12 and into the conduit 20, accumulating concentrate on the outer surface of the filter bag 22 as the sectors 12 rotate through the slurry. When the sectors 12 rotate out of the slurry, pressurized air is applied through the conduits 20 and the filter sectors 12 to cause the concentrate on the filter bag 22 to drop off into collection bins.
As a result of the highly abrasive qualities of the ore or other minerals being filtered, the filter sector 12 is subjected to abrasion and wear if any of the abrasive particles go through the filter bag 22. Various types of filter sectors have been used in disc filters, such as wooden filter sectors, metal filter sectors and plastic filter sectors. Plastic filter sectors are particularly desirable because of their resistance to corrosive materials and because of their relatively light weight.
One type of plastic filter sector 12, FIG. 2, typically includes a sector base 24 and a sector neck 26. The sector base 24 includes a number of grooves or channels 28 such that the liquid flows along the grooves or channels 28 of the sector base 24 and into the sector neck 26. To provide structural rigidity to the sector base 24, pipes 30a, 30b extend through the sector base 24. Threaded rods 32a, 32b extend through the pipes 30a, 30b and are coupled with nuts 34a, 34b to secure the sector base 24 to the sector neck 26.
Although this type of filter sector 10 is relatively lightweight and the sector body 24 resists the abrasive and corrosive effects of the slurry, a number of problems remain in the attachment of the sector base 24 to the sector neck 26. In particular, the pipes 30a, 30b extend into the flow path or region within the sector neck 26. If fine mineral particles pass through the filter bag or if a hole is formed in the filter bag, the pipes 30a, 30b are exposed to the abrasive mineral particles causing the pipes to wear through and the neck to blow out. The water and mineral particles may also seep into the pipes 30a, 30b causing corrosion within the pipes.
Another problem with this disc filter sector design is that the threaded rods 32a, 32b, extending through the pipes 30a, 30b and coupled by the nuts 34a, 34b, make the replacement of the neck 26 difficult, for example, when the abrasive mineral particles have worn through the neck 26 or the pipes 30a, 30b.
Accordingly, a need exists for a disc filter sector having an improved attachment system that facilitates attachment of the sector base to the sector neck and that is not subject to the abrasion, corrosion and other damaging effects caused by the mineral particles, concentrate or liquid. What is also desired is a filter sector in which the sector body is securely attached to the sector neck while providing a smooth flow transition between the sector base and the sector neck.